Alpha-methyl styrene/tertiary butyl styrene/olefin terepolymer resins and hot melt adhesives containing the same

ABSTRACT

Resin compositions comprising alpha-methylstyrene/tertiarybutylstyrene/olefin terpolymers, ethylene/vinyl acetate copolymer, and paraffin wax are useful as hot melt adhesives.

United States Patent [1 1 Henk et al.

[ Dec. 16, 1975 ALPHA-METHYL STYRENE/TERTIARY BUTYL STYRENE/OLEFIN TEREPOLYMER RESINS AND HOT MELT ADHESIVES CONTAINING THE SAME [75] Inventors: Michael G. Henk, Wheaten; Gary P. Sartler, Downers Grove, both of Ill.

[73] Assignee: Standard Oil Company, Chicago, lll.

[22] Filed: Aug. 12, 1974 [21] Appl. No.: 496,867

Related U.S. Application Data [62] Division of Ser. No. 418,563, Nov. 23, 1973.

[52] U.S. Cl ..260/28.5 AV; 260/285 A; 260/285 B;260/80. 7 [51] Int. Cl. C08L 91/06 58] Field of Search... 260/285 AV, 28.5 A, 28.5 B

Primary Examiner-Melvyn I. Marquis Attorney, Agent, or FirmWallace L. Oliver; Arthur G. Gilkes; William T. McClain [5 7] ABSTRACT Resin compositions comprising alphamethylsty rene/tertiary-butylstyrene/olefin terpo lymers, ethylene/vinyl acetate copolymer, and paraffin wax are useful as hot melt adhesives.

10 Claims, N0 Drawings ALPHA-METHYL STYRENE/TERTIARY BUTYL STYRENE/OLEFIN TEREPOLYMER RESINS AND HOT MELT ADHESIVES CONTAINING THE SAME This is a division of application Ser No. 418,563 filed Nov. 23, 1973.

BACKGROUND OF TI-IE INVENTION DESCRIPTION OF THE INVENTION The resin compositions of this invention are made by copolymerizing alpha-methylstyrene, tertiary-butylstyrene and a mono-olefin.

The resins of our invention can be produced in a variety of physical form s, ranging from hard resins of up to 400F ring' and ball softening point to low molecular Weight products which are viscous liquids at room temperature. The resins having a softening point up to about 350F have excellent solubility in a variety of aliphatic and aromatic organic solvents, those in the range of 200 to 350F being particularly preferred. These resins are particularly suitable for use in hot melt adhesive compositions and paper coating formulations. These resins can also be used, by routine selection of the proper ratio of components, for dry cleaning sizing purposes and for other applications which will be apparent to those skilled in the art in light of our disclosure of the properties of our resins. The resins of our invention generally have Gardner colors of one or less, which makes them especially suitable for applications requiring colorless or nearly colorless compositions, suchas in paper coating compositions.

The resins of our invention can be readily produced by catalytic polymerization of the aforementioned monomers with BF BF complexes, aluminum chloride, and similar Friedel-Crafts type acidic catalysts. This polymerization is conveniently carried out in an inert organic solvent at a temperature within the range of 60C to 100C. The softening points and molecular weight of the resins produced can be readily controlled by varying the temperature at which the monomer mixture is contacted with the catalyst, by varying the ratio of catalyst to monomers and by varying the ratio of monomer to solvent according to techniques known to the art. Generally lower temperatures produce resins of higher softening points and highermolecular weights. Higher temperatures produce resins of relatively lower softening points and lower molecular weights. While, at a given temperature, the higher the concentration of the reactants the lower the softening point and thehigher the concentration of catalyst, the lower the softening point.

The monomers used in the production of the resins of this invention are alpha-methylstyrene, tertiary-butylstyrene and an olefin. While pure alpha-methylstyrene can be used, also suitable is the commercial mixture obtained by the dehydrogenation of cumene. Such products contain from 50 to 60 percent of the monomer. The tertiary-butyl group of the tertiary-butylstyrene can be in the 3- or 4- positions; the 4- or para isomer being preferred. The presently available percent. para and 5 percent meta mixture is suitable. The olefin can be a monoor diolefin having from 2 to 12 carbon atoms including ethylene. propylene. butadiene, isoprene, 2-methyl-2-butene, and a-dodocylene. Isoprene and 2-methyl 2-butene are particularly useful in this invention and are preferred.

The proportions of monomers to be used in the preparation of the terpolymer resins can be varied from 0.1 to- 10 parts by weight of alpha-methylstyrene per part of the tertiary-butylstyrene incombination with from 0.005 to 0.5 parts per weight of olefin per part of tertiary-butylstyrene, The range of 2 to 5 parts by weight of the alpha-methylstyrene per part of the tertiary-butylstyrene in combination with from 0.01 to 0.1 parts per weight of olefin per part of tertiary-butylstyrene is preferred.

Production of our novel resins can be performed in batch or continuous operations, with the continuous process being preferred as a matter of convenience. Various inert organic solvents can be used in the polymerization processes and these provided a ready means for facilitating control of the temperatures and reaction rates of our processes. Among suitable inert organic solvents are those liquid at the temperature of reaction, such as cumene, heptanes, hexanes, toluene, xylene and the like. 1

Copolymerization is preferably carried out in a solution containing about 20 percent by weight of mixed monomers in an inert solvent such as cumene. If the monomers and solvent are not dry, the solution for polymerization can be dried by percolation through calcium chloride or by other means known to the art. The polymerization feed can then be cooled to a desired inlet temperature and pumped into a tubetype reactor, the gaseous BF bei'ng metered into the feed as it enters the reactor. Solvent and catalyst can be removed from the resin by distillation techniques well known to the art.

An area of utility which we consider has special value is the use of these resins in ethylene-vinyl acetate/petroleum wax composition.

The utilization of alpha-methylstyrene/tertiary-butylstyrene/olefin terpolmers produced as set forth above have been found to impact excellent properties of heat stability, color, odor, and performance to the ethylenevinyl acetate/petroleum wax compositions used as hot melt adhesives. Furthermore, the wide range of compatibility of the modifying agent in the blends allows choice of blends to meet the individual needs of various applications without sacrificing the major advantages. In addition, the copolymers have unexpectedly been found to have advantages over the prior art modifiers since they possess properties of easier blending, higher clarity, lower viscosity, superior heat-seal properties, and better flexibility.

Although homopolyers of alpha-methylstyrene are not particularly suited to a broad range of applications in conjunction with ethylene-vinyl acetate copolymer hot melt systems because of too little compatibility, it is recognized in the art that copolymers, particularly alpha-methylstyrene/tertiary-butylstyrene, have been found to offer a wider selection of compatibility to suit the specific end-use requirements. Thus, increasing quantities of copolymerized tertiary-butylstyrene will result in improved wax compatibility. Typically, an alpha-methylstyrene/tertiary-butylstyrene copolymer with monomer ratio of 2/ 1 respectively has a ring and ball softening point of 240F and a cloud point (a measure of the compatibility) of about 330F. A similarly prepared terpolymer. of this invention will achieve properties at a far lower concentration of tertiarybutylstyrene. For example, an alpha-methylstyrene/tertiary-butylstyrene/Z-methyl-2-butene terpolymer with a weight ratio of 3/l/.05 respectively will also have a softening point of 240F and a cloud point of about 330F.

The effect of the presence of the olefin on the amount of tertiary-butylstyrene required to achieve the desired wax compatibility of the resulting resin is of such magnitude that the breadth of the molecular weight distribution of the resin becomes a secondary consideration and can be readily controlled. It is known that narrowing the molecular weight distribution improves the wax compatibility of the polymer. Thus, commercially an isothermal process is usually preferred. However, for the monomer system disclosed herein, an adiabatic process, without cooling facilities, yields resins of excellent physical properties with superior wax compatibilities over a wide range of monomer concentrations. The use of the olefin imparts such flexibility to the choice of polymerization conditions that the molecular weight of the final resins can be controlled by choice of concentration of reactants even within an adiabatic process. In addition the resulting terpolymers are more heat stable and less temperature sensitive than the alpha-methylstyrene copolymers without the olefin.

Briefly. the adhesive compositions of this invention comprises an ethylene-vinyl acetate copolymer, a petroleum wax, and the alpha-methylstyrene/tertiarybutylstyrene/olefin terpolymer. Because of the wide range of compatibility, any ethylene-vinyl acetate copolymer or petroleum wax known to the wt for use in hot melt compositions, may be utilized in this invention. More specifically, the composition comprises, per 100 parts by weight of the alpha-methylstyrene terpolymer, to 1200 parts of the ethylene-vinyl acetate copolymer and 10 to 1800 parts of the paraffin wax. Generally, the ethylene-vinyl acetate copolymer should comprise between and 40 weight percent copolymerized vinyl acetate, advantageously between and 35 weight percent and preferably between and weight percent. Consequently, the copolymerized ethylene content will be between 60 and 85 weight percent. advantageously between 65 and 80 weight percent and preferably between 70 and 75 weight percent. The molecular weight of the ethylene-vinyl acetate copolymer may vary over a fairly broad range since acceptable performance may be obtained by varying the molecular weight distribution in relation to the molecular weight. The molecular weight, expressed in terms of melt flow (ASTM D-l238-57T) should be less than 50, advantageously 1-30 and preferably ll 2. Such resins are well known and commercially available.

CHANGE SOLVENT The petroleum waxes which may be used in this invention include both paraffin and microcrystalline waxes having a melting point in the range of about l25-l75F and l50200F. respectively. Mixtures of various waxes are also suitable. A preferred class of petroleum wax is the paraffin wax, having a melting point of between and F.

Preparation of the compositions of this invention may be accomplished by thoroughly blending the components at an elevated temperature. The agitation or mixing may be accomplished by an conventional high shear mixer, the only requirement being that the components be thoroughly blended so as to provide a uniform composition. It is desirable that the compositions be prepared at a temperature in the range of about 300 to 350F. This range is chosen since the ethylene-vinyl acetate copolymer becomes quite unstable above 400F. In addition, it has been found desirable to add an antioxidant during the blending in order to allow sufficient time to blend at the temperatures indicated. Suitable antioxidants are 2,6-di-tertbutyl-p-cresol, and 4,4-methylene-bis( 2,6-di-teItbutylphenol Compositions of this invention may be coated by any conventional coating system for high viscosity hot melts, or if they are to be used as adhesives any conventional adhesive applicator can be utilized. It has been found particularly desirable to maintain the composition at a temperature of from 300 to 350F when coating by means of a roll coater.

The following examples illustrate specific embodiments of my invention but should not be considered unduly limiting.

EXAMPLES l to XI A series of six alpha-methylstyrene/tertiary-butylstyrene/olefin terpolymers and five alpha-methylstyrene/tertiary-butylstyrene copolymers were prepared by either batch or continuous polymerization. The data relating to the polymerization and characterization of the product are presented in Table l.

' For the batch polymerization method an approximately 1000 gram sample of a 80 weight percent solvent was percolated through a bed of anhydrous CaCl and then transferred to a three-necked flask having a stirrer and a thermocouple. The stirred solution was then cooled to below the desired initiation temperature. The cooling bath was then removed and the solution was allowed to slowly warm to the desired initiation temperature. Upon reaching the initiation temperature, BF catalyst was added and the reaction was allowed to go to completion. During polymerization the time. and temperature was monitored. Upon completion the BE, and solvent were removed by distillation with the use of nitrogen sparge at atmospheric pressure until the solution temperature reached approximately 200C. A house vacuum (=25 torr) was used between 200C and 245C until devolatilization visually stopped. The remaining volatiles in the resins as measured by gas chromatography were generally less than 60 0.1 percent.

TABLE I PHYSICAL PROPERTIES OF RESIN INITIATION TEMP. RING & BALL CLOUD" MOLECULAR WEIGHT EX. RELATIVE PARTS BY TEMP. 1C) T(C) SOFI'ENING POINT WEIGHT AMS' TBS OLEFIN" POINT Mn Mw Mz I 3 l 0.05 9 41 Toluene 253 350 1079 2710 5700 II 3 1 0.05 9 37 Toluene 242 364 968 2740 6l00 TABLE I-continued CHANGE SOLVENT INITIATION TEMP. RING & BALL CLOUD MOLECULAR WEIGHT EX. RELATIVE PARTS BY TEMP. (C) T(C) SOFTENING POINT WEIGHT AMS TBS OLEFIN POINT Mn Mw Ml.

III 3 I 0.05" 1 45 Toluene 235 362 951 2590 5900 IV 3 l 0.05" 8 32 Toluene 243 322 951 2430 5000 V 3 I 0.05 l0 Toluene 249 256 1058 2390 4600 VI 3 I 0.04 -10 50 Cumenc 234 332 913 I830 VII 2 I None l() 46 Cumenc 242 332 I089 I830 VIII 2 I None --8 43 Cumene 239 334 929 2820 8200 IX 3 1 None 8 44 Cumene 218 450 869 2930 8600 X 3 I None 7 32 Cumene 240 370 960 2730 9400 XI 3 I None 7 33 Cumene 243 440 924 2620 7400 alphu-methylslyrene "tertiary butylstyrene "either iso rene ur lmethyl-Z-hutene" ASTM EZX-SIT Cloud Point ofa blend of AMS, TBS cnpolymer/eth lene-vinyl acetate copol mer/purallin wax in weight ratio of 100100.300. I Elvnx 260 containing 28''; \'in \l acetate (Eel Permeation Chromatograph For the continuous polymerization method a sample in excess of 10,000 grams of monomer/solvent feed was prepared in a manner similar to the batch runs. The feed was pumped at a rate of 60 cc per minute through a cooling coil submerged in a constant temperature bath and then through a tube reactor where it was contacted with the BE; catalyst. The solvent and catalyst removal after polymerization was similar to the previous batch experiments.

Examples I through V1 are typical of the softening point and cloud point values achieved at a 3/l/0.05 ratio of alpha-methylstyrene/tertiary-butylstyrene/olefin. These values are more closely analogous to the typical values for a 2/1 ratio of alpha-methylstyrene/- tertiary-butylstyrene as seen in Examples VII and VIII than the values typical of a 3/1 ratio as seen in Examples IX through XI. Thus exemplifying the ability of trace amounts of olefin to increase the wax compatibility of an alpha-methylstyrene/tertiary-butylstyrene polymer at far lower levels of tertiary-butylstyrene than previously known. Although the mechanism by which this is accomplished is not fully understood, one possible interpretation is that the presence of the trace amounts of olefin enhance the tertiary-butylstyrenes ability to copolymerize with increased randomness thus decreasing the frequency of long chain homopolymer blocks of wax-incompatible poly alpha-methylstyrene.

EXAMPLE XII The terpolymer resins of the previous examples when blended in the following formulation:

Component Parts by Weight terpolymer 100 ethylene/vinyl acetate cop0lymer* I00 paraffin wax 300 microcrystalline wax I67 values in excess of 300 b/10 cm. The moisture vapor transmission rates are similar. While the terpolymer displays excellent heat stability in that no separation occurs after hours at 350F with only slight color change.

We claim:

1. A composition comprising a terpolymer consisting of:

a. one part by weight tertiary-butylstyrene;

b. from 1 to 10 parts by weight alpha-methylstyrene'.

and

from 0.005 to 0.5 parts by weight of olefin having a ring and ball softening point of 200 to 350F. and, per 100 parts by weight of said terpolymer. 10 to 1200 parts of an ethylenevinyl acetate copolymer having a vinyl acetate content within the range of 15 to 40 weight percent, and 10 to 1800 parts of a paraffin wax having a melting point of to 200F.

2. The composition of claim 1 containing, per 100 parts by weight of said terpolymer 100 parts of said ethylene-vinyl acetate copolymer and 300 parts of said paraffin wax.

3. The composition of claim 1 wherein the terpolymer consists of by weight one part tertiary-butylstyrene, from 2 to 5 parts alpha-methylstyrene, and from 0.01 to 0.1 parts olefin.

4. The composition of claim 3 wherein the ethylenevinyl acetate copolymer has a vinyl acetate content within the range of 25 to 30 weight percent.

5. The composition of claim 3 wherein the olefin is selected from the group consisting of isoprene and 2-methyl-2-butene.

6. The composition of claim 4 wherein the olefin is selected from the group consisting of isoprene and Z-methyI-Z-butene.

7. The composition of claim 3 containing per 100 parts by weight of terpolymer, 100 parts of ethylenevinyl acetate copolymer and 300 parts of paraffin wax.

8. The composition of claim 6 containing per 100 parts by weight of terpolymer, 100 parts of ethylenevinyl acetate copolymer and 300 parts of paraffin wax.

9. The composition of claim 7 wherein the terpolymer consists of by weight one part tertiary-butylstyrene, about 3 parts alpha-methylstyrene and about 005 parts of an olefin selected from the group consisting of isoprene and Z-methyI-Z-buten'e.

10. The composition of claim 9 wherein the tertiarybutylstyrene is at least 90 percent the para isomer. 

1. A COMPOSITION COMPRISING A TERPOLYMER CONSISTING OF: A. ONE PART BY WEIGHT TERTIARY-BUTYLSTYRENE; B. FROM 1 TO 10 PARTS BY WEIGHT ALPHA-METHYLSTYRENE; AND C. FROM 0.005 TO 0.5 PARTS BY WEIGHT OF OLEFIN HAVING A RING AND BALL SOFTENING POINT OF 200* TO 350*F. AND, PER 100 PARTS BY WEIGHT OF SAID TERPOLYMER, 10 TO 1200 PARTS OF AN ETHYLENEVINYL ACETATE COPOLYMER HAVING A VINYL ACETATE CONTENT WITHIN THE RANGE OF 15 TO 40 WEIGHT PERCENT, AND 10 TO 1800 PARTS OF A PARAFFIN WAX HAVING A MELTING POINT OF 125* TO 200*F.
 2. The composition of claim 1 containing, per 100 parts by weight of said terpolymer 100 parts of said ethylene-vinyl acetate copolymer and 300 parts of said paraffin wax.
 3. The composition of claim 1 wherein the terpolymer consists of by weight one part tertiary-butylstyrene, from 2 to 5 parts alpha-methylstyrene, and from 0.01 to 0.1 parts olefin.
 4. The composition of claim 3 wherein the ethylene-vinyl acetate copolymer has a vinyl acetate content within the range of 25 to 30 weight percent.
 5. The composition of claim 3 wherein the olefin is selected from the group consisting of isopreNe and 2-methyl-2-butene.
 6. The composition of claim 4 wherein the olefin is selected from the group consisting of isoprene and 2-methyl-2-butene.
 7. The composition of claim 3 containing per 100 parts by weight of terpolymer, 100 parts of ethylene-vinyl acetate copolymer and 300 parts of paraffin wax.
 8. The composition of claim 6 containing per 100 parts by weight of terpolymer, 100 parts of ethylene-vinyl acetate copolymer and 300 parts of paraffin wax.
 9. The composition of claim 7 wherein the terpolymer consists of by weight one part tertiary-butylstyrene, about 3 parts alpha-methylstyrene and about 0.05 parts of an olefin selected from the group consisting of isoprene and 2-methyl-2-butene.
 10. The composition of claim 9 wherein the tertiary-butylstyrene is at least 90 percent the para isomer. 